Bioabsorbable Stent Corrosion Control via Hydrothermal Film
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Solution Overview
Problem
Magnesium alloy stents corrode too quickly for effective use in medical applications, and existing methods to slow corrosion, such as anodization, are ineffective and time-intensive, especially for complex geometries like stents with high surface area to volume ratios.
Innovation Solution
A bioabsorbable stent is developed with a hydrothermal conversion film and a polymer coating, where the hydrothermal film, typically made of magnesium oxide, is applied to the magnesium alloy stent, and a biodegradable or non-biodegradable polymer coating is applied over the film to slow corrosion, with the option of a biodegradable atomic layer deposition coating for enhanced protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnesium alloy is used for bioabsorbable stent, then biocompatibility and degradation capability are improved, but corrosion rate increases too quickly
Solution Approach 1:
The patent applies composite materials by combining magnesium alloy with multiple coating layers including hydrothermal conversion films and polymer coatings. This composite structure allows the base magnesium alloy to provide biocompatibility and degradation capability while the coating layers provide corrosion resistance, resolving the contradiction between rapid corrosion and desired durability.
2Duration of action of stationary object
If anodization is applied to slow corrosion, then corrosion rate is reduced, but manufacturing time and complexity increase significantly
Solution Approach 1:
The patent employs hydrothermal treatment which changes the chemical parameters (temperature, pH, composition) to form a protective conversion film more rapidly than anodization. This process achieves corrosion protection through chemical transformation rather than prolonged electrochemical processing, significantly reducing manufacturing time while maintaining effectiveness.
3Duration of action of stationary object
If hydrothermal film is applied to metal sample, then corrosion rate is slowed, but film thickness becomes too large for stent application
Solution Approach 1:
The patent applies hydrothermal treatment under controlled conditions to form a thin conversion film that provides sufficient corrosion protection without excessive thickness. By optimizing treatment parameters (time, temperature, solution composition), the process achieves the minimum necessary protection while avoiding the thick films that would be problematic for stent geometry and flexibility.
4Duration of action of stationary object
If thick hydrothermal film is formed, then corrosion protection is enhanced under static conditions, but flexibility and dynamic performance are reduced
Solution Approach 1:
The patent optimizes hydrothermal treatment parameters to form thin films that maintain stent flexibility. By controlling film thickness through parameter adjustment, the solution achieves adequate corrosion protection while preserving the mechanical flexibility required for stent deployment and function in dynamic physiological conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The combination of hydrothermal conversion films and polymer coatings effectively delays corrosion of magnesium alloy stents for several weeks to months, maintaining mechanical integrity for 3-6 months and complete degradation within a year, while withstanding dynamic conditions and ensuring uniform corrosion.
Implementation Method 1
During the hydrothermal process, a hydrothermal conversion film (hydrothermal film) is formed on the surface of the metal sample and acts as a barrier to slow down the rate of corrosion of the metal sample
Implementation Method 2
a coating covering the hydrothermal conversion film
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A stent includes a bioabsorbable metal, a hydrothermal conversion film covering the bioabsorbable metal, and a coating covering the hydrothermal conversion film. A method for manufacturing a stent includes forming a stent body comprising a bioabsorbable metal, forming a hydrothermal conversion film over surfaces of the stent body, and coating the hydrothermal conversion film with an overcoat.